Preparation of acrylonitrile fibers



United States Patent 3,149,039 PREPARATION OF ACRYLONITREE FIBERS Anson M. Hayes, Wayneshoro, Va, assignor to E. I. du Pont de Neinours and Company, Wilmington, Del, a corporation of Delaware N0 Drawing. Filed Aug. 27, I359, Ser. No. 836,339 ll) Claims. (ill. loll-32.6)

This invention relates to the preparation of acrylonitrile fibers. More particularly, it relates to new compositions of matter containing acrylonitrile polymers which are capable of being spun into fibers having a high degree of luster stability.

In the preparation of textile materials, acrylonitrile fibers which have an initial uniform luster have been produced. However, in the absence of some special treatment, such fibers generally tend to lose their luster during normal textile processing operations. For example, the initially lustrous fibers usually become somewhat delustered on exposure to the hot-wet conditions utilized in washing, steam pressing, bleaching, and dyeing of the fabrics, yarns, rovings, staple, or other fiber forms. This loss of luster is generally observed as a dulling in an undyed material, or dulling and lightening of dye shades in I dyed materials. It is especially objectionable where nonuniformities occur in a single textile article as a result of localized variations in the treating conditions.

Although the problem of loss of luster is not fully understood, according to one hypothesis,delustering is at least partially attributable to the presence of traces of solvent in the freshly manufactured fibers. Variations in the solvent level would therefore lead to nonuniform delustering. 7

As previously indicated, special treatments can be utilized to reduce the severity of this problem; however, such treatments have not proved to be entirely satisfactory. Methods for improving luster stability of the fiber by removal of all traces of the solvent used in fiber preparation have proven to be too expensive to be commercially feasible. Dyeing techniques in whichincreased amounts of dyes are utilized to provide a desired coloration in the delustered fibers are also costly.

It is, therefore, an object of this invention to provide fibers of polymers of acrylonitrile which have a high initial luster. Another object of this invention is to provide lustrous acrylonitrile fibers which retain a high degree of luster during normal textile processing and use. A further object of this invention is to provide a homogeneous solution capable of being spun into fiberswhich have a lasting luster.

wherein R and R represent haloalkoxy radicals having 1 to 5 carbon atoms in the alkyl chain and from 1 to 4 substituted halogen atoms on the chain, and R is selected from the group consistingof hydroxyl and haloalkoxy radicals of the type just described, the combined total of said halogen atoms in the haloalkyl phosphate being at least 3. The spinning solution described is then extruded through orifices of a spinneret to form fibers according to known procedures.

Surprisingly, by adding as little as about 3% of the haloalkyl phosphate, based on the Weight of the polymer in the spinning solution, improved stability in luster is ice obtained. Amounts from about 5% to about 15% have been found to provide optimum results. Amounts in excess of above 20% should be avoided since they tend to cause deterioration of other properties of the fibers such as tenacity, modulus, and wet strength. It is also surprising that the addition of the haloalkyl phosphate does not have a deleterious effect on other physical properties of the fibers since the addition of materials other than copolymerizable monomers generally results in markedly lower physical properties. In addition to the improved luster stability, it has been found that improved spinning properties are obtained by adding the haloalkyl phosphate to the spinning solution. A lower amount of solvent may be included in the solution as compared to that obtainable when the solution does not include the phosphate ester. This facilitates the spinning of heavy denier filaments.

In practicing the present invention, an acrylonitrile polymer may be prepared in a conventional manner such as that described in U.S. 2,628,223, U.S. 2,748,106, or U.S. 2,777,832. A homogeneous solution containing from about 5% to about 35% byweight of the polymer in an inert solvent is then prepared.- Any of the known organic and inorganic solvents which are inert to the polymer may be used. Selection of the particular solvent Will generally depend on Whether a Wetor dry-spin ning technique is being used. In the dry-spinning process, organic solvents such as dimethylformamide dimethylacetamide, dimethyl rnethoxy-acetamide, N-formyl morpholine, N-formyl hexamethyleneimine, butadiene cyclic sulfone, tetramethylene cyclic sulfone, p-phenylene diamine, mand p-nitrophenols, and the like, may be used. in the. Wet-spinning process, inorganic solvents such as metal halides and thiocyanates, and those salts and mixed salts described in U.S. Patents 2,648,646 through 2,648,649 may be used. From about 3% to about 20%, based on the Weight of the polymer, of the phosphate ester is then added to the solution. ternatively, the phosphate ester may be added simultaneously with or prior to the addition of the solvent, or to the freshly spun, solvent-laden filaments either prior to or.

during drawing and extraction. A stabilizer for the phosphate ester, for example a compound which will react with hydrogen halide, such as a base, an active ethylenic compound, an epoxy compound and the like,

may be added to the spinning solution or to the treating solution containing the phosphate ester.

In determining the degree of luster of a fiber, a number of known methods may be used. In a preferred method, a number of strands are Wrapped onto a rectangular frame. The frame is then immersed in a'material having a refractive index similar to that of the fibers to eliminate surface effects. The light transmitted through the fibers on the frame is then measured. Anisole has been found to be a suitable liquid for use with acrylonitrile polymer fibers. The degree of luster of various fiber samples can be conveniently computed by using the filter With peak transmission at 4200 A. Fibers having a luster of above are not considered appreciably delustered, while values of 60 and below represent appreciable delustering.

The degree of delustering can be determined in dyed goods by observing the effectiveness of a given amount of dye in furnishing coloration. Deeper and brighter shades are obtained from fibers which are not delustered. Changes in fiber density are also indicative of changes in luster. In general, a high luster is associated with a high density.

The invention is further illustrated by reference to the following examples in which parts and percentages are by weight unless otherwise indicated.

EXAMPLE I Ten parts of a polymer of 93.6% acrylonitrile, 6% methyl acrylate, and 0.4% sodium styrene-sulfonate, prepared by emulsion polymerization with a persulfate/ bisulfite redox catalyst system, were mixed under nitrogen with 20 parts dimethylformamide at a temperature of 50 C. with continuous stirring until a homogeneous solution was obtained. A haloalkyl phosphate was subsequently mixed into the homogeneous polymer solution; the nature and amount of haloalkyl phosphate being indicated by the data for separate experimental runs listed in the following table. The mixture was then spun at a temperature of 100 C. through a spinneret having 0.15 mm. holes at a rate of 900 feet per minute downward into a tube 18 feet long and of 8-inch diameter containing a cocurrent flow of nitrogen at 250 C. The fibers leaving the tube still wet with solvent were subsequently led through a hot water bath, wherein the fibers were washed and drawn three times their original length. The washed fibers were then dried at a temperature of 125 C. for nine minutes, yielding lustrous, strong fibers containing 2-3% residual solvent. To test the stability of the luster to hot-wet conditions, fibers prepared with each different haloalkyl phosphate were immersed in a boiling 0.1% aqueous solution of Tide, 2. commercial detergent manufactured and sold by Proctor and Gamble, Cincinnati, Ohio, for ten minutes. The fibers were then rinsed with pure water and dried at room temperature. Determination of luster was by the method previously described in col. 2.

*T/E=Tenacity (grams per denier) [elongation (percent).

It is apparent from the data in the above table that fibers prepared by the addition of halo-alkyl phosphates to the fiber spinning solution produce luster-stable fibers without impairing physical properties.

EXAMPLE H A polyacrylonitrile fiber was prepared as in Example I except that the haloalkyl phosphate was not added to the spinning solution. The fibers leaving the tube still wet with solvent were subsequently led through a bath at 80 C. containing 20% tris(2,3-dibromopropyl)phosphate and 10% tertiary butanol as a wetting agent, and water and were drawn four times their original length. An absorption of of the haloalkyl phosphate was obtained. The treated fibers were then tested for luster stability by the same procedure used in Example I. The results obtained were as follows: Luster value, before boiling=90; after boiling=85.

It is evident that luster stability is imparted to these fibers by incorporating the additive by drawing the still solvent-laden yarn in a bath containing the haloalkyl phosphate.

As previously indicated, from about 5% to about 15% haloalkyl phosphate, based on the Weight of polymer, provides optimum results. The haloalkyl phosphates are generally completely miscible with the polymer at these levels of addition and yield clear, homogeneous fibers having unimpaired physical properties. However, haloalkyl phosphates which are slightly soluble, i.e., have a solubility up to about 0.5% in Water, confer permanent luster stability to the fibers when used according to the process of this invention.

In addition to the haloalkyl phosphates heretofore exemplified, other phosphate esters may be substituted in like amounts for those set forth in the examples. For example, the alkoxy groups may be selected from chloro-, iluoro-, and bromo-substituted methyl, ethyl, propyl, isopropyl, butyl, isobutyl, or tertiary butyl, and may be the same or different. Typical examples include tris-chloroethyl phosphate, tris-bromoethyl phosphate, chloro ethyl monopropyl phosphate, and 2,3-bromopropyl phosphoric acid. The bromoalkyl phosphates are generally preferred to the corresponding fluorine or chlorine compounds since they appear to provide better luster stabiliz ing properties and exhibit greater compatibility with polyacrylonitrile.

As previously indicated, spinning solutions containing acrylonitrile polymers in which the acrylonitrile component comprises at least of the polymer molecule may be prepared by the process of this invention. These polymers may contain one or more ethyleuically unsaturated monomers which are copolymerizablc with acrylonitrile. Examples of typical copolymerizable monomers are well known and may be found in US. Patents 2,436,926, 2,485,241, and 2,837,501. The polymers should preferably have an average molecular weight in the range of 40,000 to 150,000, and generally the molecular weight should be above 15,000 and should not exceed the value of 250,000.

One of the primary advantages of the present invention resides in providing spinning solutions which may be extruded under pressure through a spinneret orifice to yield acrylonitrile fibers which have an initial uniform luster which remains substantially unchanged during subsequent processing. Another advantage residcs in the fact that the fibers prepared from the spinning solutions of this invention have high physical properties typical of fibers prepared from acrylonitrile polymers. In addition to the improved luster stability and retention of high physical properties, spinability of the polymer solutions is improved, thus permitting a lower percentage of solvent in the solution as compared to spinning solutions heretofore known.

It will be apparent that many'widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. As a new composition of matter a homogeneous spinning solution comprising an acrylonitrile polymer selected from the group consisting of homopolymers of acrylonitrile and copolymers containing at least 70% acrylonitrile and up to 30% by Weight of an ethylenically unsaturated monomer copolymerized therewith, an inert solvent for said polymer, and from about 3% to about 20% based on the weight of said polymer of a haloalkyl phosphate having the general formula wherein R R and R are haloalkoxy radicals having alkyl radicals selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tertiary butyl, and from 1 to 4 substituted halogen atoms selected from the group consisting of bromine and chlorine.

2. The composition of claim 1 in which the haloalkyl phosphate is tris(2,3-dibromopropyl)phosphate.

3. The composition of claim 1 wherein said solution contains from about 5% to about 35% by weight of said polymer.

4. The composition of claim 1 in which said polymer contains at least 85% acrylonitrile by weight in polymerized form and said solvent is N,N-dimethylforrnamide.

5. A process for preparing filaments having a high degree of luster stability which comprises extruding a solution of an acrylonitrile polymer selected from the group consisting of homopolymers of acrylonitrile and copolymers containing at least 70% acrylonitrile, and up to by Weight of an ethylenically unsaturated monomer copolymerized therewith, containing from about 5 to about by weight of said polymer to form said filaments, treating said filaments in an aqueous bath containing from about 5% to about 20% of a haloalkyl phosphate having the general formula wherein R R and R are haloalkoxy radicals having alkyl radicals selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tertiary butyl and from 1 to 4 substituted halogen atoms selected from the group consisting of bromine and chlorine, for a period suflicient to permit said filaments to absorb from about 5% to about 15% by weight of said haloalkyl phosphate, and thereafter removing said filaments from said bath.

6. The process of claim 5 wherein said phosphate is tris (2,3-dibromopropyl)phosphate.

7. The process of claim 5 wherein said polymer is dissolved in N,N-dimethylformamide.

8. The process of claim 5 wherein said polymer contains at least 85% acrylonitrile by weight in polymerized form.

9. A process for preparing filaments having a high degree of luster stability which comprises extruding a homogeneous solution comprising from about 5% to about 35% by weight of a polymer containing at least acrylonitrile in polymerized form, an inert solvent for said polymer, and from about 3% to about 20% based on the weight of said polymer of a haloalkyl phosphate having the general formula Ra wherein R R and R are haloalkoxy radicals having alkyl radicals selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl and tertiary butyl and from 1 to 4 substituted halogen atoms selected from the group consisting of bromine and chlorine washing said filaments in an aqueous bath whereby said solvent is substantially removed from said filaments, and thereafter drying said filaments.

10. A filament comprising an acrylonitrile polymer se- I lected from the group consisting of homopolymers of acrylonitrile and copolymers containing at least 70% acrylonitrile and up to 30% of an ethylenically unsaturated monomer copolymerized therewith having included therein from about 5% to about 15% by weight of a haloalkyl phosphate having the general formula wherein R R and R are haloalkoxy radicals having alkyl radicals selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tertiary butyl and from 1 to 4 substituted halogen atoms selected from the group consisting of bromine and chlorine.

References Cited in the file of this patent UNITED STATES PATENTS 1,985,771 Eichengrun Dec; 25, 1934 2,642,408 Stanin et a1 June 16, 1953 2,773,046 Dunn et a1 Dec. 4, 1956 2,996,474 Voigt Aug. 15, 1961 FOREIGN PATENTS 700,292 Great Britain Nov. 25, 1953 

1. AS A NEW COMPOSITION OF MATTER A HOMOGENEOUS SPINNING SOLUTION COMPRISING ACRYLONITRILE POLYMER SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYMERS OF ACRYLONITRILE AND COPOLYMERS CONTAINING AT LEAST 70% ACRYLONITRILE AND UP TO 30% BY WEIGHT OF AN ETHYLENICALLY UNSATURATED MONOMER COPOLYMERIZED THEREWITH, AN INERT SOLVENT FOR SAID POLYMER, AND FROM ABOUT 3% TO ABOUT 20% BASED ON THE WEIGHT OF SAID POLYMER OF A HALOALKYL PHOSPATE HAVING THE GENERAL FORMULA 